(1) Field of the Invention
This invention relates to a process for excavating and constructing a tunnel and an excavating device therefor, and more particularly to a process for constructing a tunnel under a railway or road in the direction transverse thereto.
(2) Description of the Prior Art
Hithereto, for excavating a tunnel under a railway, road or a building in the direction transverse thereto, several attempts are known, such as a shielding process or a process, in which steel pipes are driven into the ground above a tunnel or along the upper-arcuate portion of the tunnel in the longitudinal direction of the tunnel, and then soil or sand therein are excavated by towing an excavator, after which a tunnel is constructed internally of the cavity thus formed. However, the former attempt suffers from disadvantages of an excessively large scale excavating device and an expenditure of much time and efforts for placing segments after the excavation, and the like. The latter attempt, on the other hand, poses problems that considerable long steel pipes should be driven at a considerable depth under the surface of the ground in the horizontal direction, and as a result a large area is required for constructing of the tunnel. In addition, difficulties are encountered with driving steel pipes into the ground in precisely side-by-side relation along predetermined paths. Furthermore, when an excarator is towed through the ground encompassed with steel pipes driven, the excavator does not happen to leave an ample thickness of soil between the top row of steel pipes and the excavator, thus presenting a danger of ground subsidence.